The invention relates to trolleys and more particularly to trolleys for transporting or conveying prepared foods with cooling and/or warming thereof. The trolleys are ud, for example, in hospitals and retirement homes and in various means of public transportation.
A trolley of this type is already known from FR-A-2 684281 and from WO-97/09575. The trolley comprises a casing with a heat insulating wall inside which the food dishes are mounted. Means are provided for defining a first zone and a second zone, and these defining means may be a heat insulating partition or may be a virtual partition represented by the fact that the food dishes are covered with a dish-cover made of a heat insulating material, all the parts under the dish-cover on the one side of the trolley representing the first zone and on the other side the second zone. The first zone is generally designed to receive part of the dishes on which food is deposited intended to be consumed cold. It consists of a zone which must be kept at a low temperature, usually at around 3xc2x0 C. On the other hand, the second zone is intended to receive food which must be consumed hot. This zone is first of all kept at a cold temperature of 3xc2x0 C. for example, and then before the meal is consumed, is brought to a higher temperature, in particular 65xc2x0 C. so that the food is reheated and may be served hot. To this end, the trolley includes a first device for cooling the first zone, a second device for cooling the second zone and a device for heating the second zone.
The disadvantage of trolleys known up to now is that devices for cooling by a refrigerating fluid or by absorption, both for the first zone as well as for the second zone, are operating as soon as they are put onto the trolley, even though they are not to be used at this time. As they can only provide a limited cooling capacity, they must be put on the trolley at the last moment or adapted to have the capacity to provide less cooling, so that the trolley can only keep food cold for a shorter time.
According to the invention, each cooling device comprises a first container for a gas, and optionally a first solid reagent capable of reacting with the gas, and a second container for a second solid reagent capable of reacting with the gas and which, if a first solid reagent is provided, is able to react more vigorously with the gas than the first solid reagent. The containers communicate with each other via a conduit provided with a valve. The first container of the first cooling device is placed in the first zone, while the second container of the first cooling device is placed outside the two zones. The first container of the second cooling device is placed in the second zone, while the second container of the second cooling device is placed outside the two zones.
The cooling devices operate by a thermochemical process, and they are actuated when the valve is opened. In this manner, the capacity of the cooling devices to produce cooling is only used deliberately and selectively.
According to one particularly preferred embodiment, the heating device comprises a first reservoir for a gas and optionally a first solid product able to react with the gas and a second reservoir for a second solid product able to react which, if a first solid product is provided, is able to react more vigorously with the gas than the first solid product, communicating with each other via a conduit provided with a valve, the first reservoir being placed outside the two zones, while the second reservoir is placed in the second zone.
The same advantages are thus obtained for the heating device as for the cooling devices, with the supplementary advantage that since the heating device is in this case entirely self contained and mounted on board the trolley, it is possible to operate it in at any moment whatsoever without being dependent on a source of electrical power at a fixed point. The heating can be started while the food dishes are carried in the trolleys. This enables the waiting time to be reduced.
In accordance with a second embodiment, it is possible to individualize more satisfactorily the cooling and/or heating of prepared dishes placed on the various plates. To that end, individual cooling and/or heating zones are provided for each prepared dish in order to obtain individual cooling or individual cooling and/or heating.
The gas may be ammonia or its derivatives, in particular alkylamines with C1 to C8, for example monomethylamine, dimethylamine, but also water, CO2, SO2, SO3 or H2. The solid adsorbent reagent may be a salt, such as a halide, a pseudohalide, a carbonate, a sulfate, a nitrate, an oxide or a metallic nitride, which, preferably, is in a natural expanded graphite matrix. The endothermicity of the reaction gives the desired cooling. As metals of salts constituting the solid reagents, use may in particular be made of the salts of the alkaline earth metals, zinc salts, manganese salts, iron salts and nickel salts. As a salt, reference may in particular be made to MnCl2, SrCl2, SrBr2 to maintain the temperature at 3xc2x0 C. and NiCl2, MgCl2, MgBr2 and NiBr2 to maintain the temperature at xe2x88x9220xc2x0 C. When couples of reagents or solid products are provided, these may be for example NICl2, MgCl2, MgBr2, NiBr2, NiCl2, NiBr2 according to the desired temperatures.